Rice cultivar L-207

ABSTRACT

A rice cultivar designated L-207 is disclosed. The invention relates to the seeds of rice cultivar L-207, to the plants of rice L-207 and to methods for producing a rice plant produced by crossing the cultivar L-207 with itself or another rice variety. The invention further relates to methods for producing a rice plant containing in its genetic material one or more transgenes and to the transgenic rice plants and plant parts produced by those methods. This invention also relates to rice cultivars or breeding cultivars and plant parts derived from rice cultivar L-207, to methods for producing other rice cultivars, lines or plant parts derived from rice cultivar L-207 and to the rice plants, varieties, and their parts derived from the use of those methods. The invention further relates to hybrid rice seeds and plants produced by crossing the cultivar L-207 with another rice cultivar.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinctive rice cultivar designated L-207. All publications cited in this application are herein incorporated by reference.

Rice is an ancient agricultural crop and is today one of the principal food crops of the world. There are two cultivated species of rice: Oryza sativa L., the Asian rice, and O. glaberrima Steud., the African rice. O. sativa L. constitutes virtually all of the world's cultivated rice and is the species grown in the United States. Three major rice producing regions exist in the United States: the Mississippi Delta (Arkansas, Mississippi, northeast Louisiana, southeast Missouri), the Gulf Coast (southwest Louisiana, southeast Texas), and the Central Valleys of California.

Rice is a semi-aquatic crop that benefits from flooded soil conditions during part or all of the growing season. In the United States, rice is grown on flooded soils to optimize grain yields. Heavy clay soils or silt loam soils with hard pan layers about 30 cm below the surface are typical rice-producing soils because they minimize water losses from soil percolation. Rice production in the United States can be broadly categorized as either dry-seeded or water-seeded. In the dry-seeded system, rice is sown into a well-prepared seed bed with a grain drill or by broadcasting the seed and incorporating it with a disk or harrow. Moisture for seed germination is from irrigation or rainfall. For the dry-seeded system, when the plants have reached sufficient size (four- to five-leaf stage), a shallow permanent flood of water 5 to 16 cm deep is applied to the field for the remainder of the crop season.

In the water-seeded system, rice seed is soaked for 12 to 36 hours to initiate germination, and the seed is broadcast by airplane into a flooded field. The seedlings emerge through a shallow flood, or the water may be drained from the field for a short period of time to enhance seedling establishment. A shallow flood is maintained until the rice approaches maturity. For both the dry-seeded and water-seeded production systems, the fields are drained when the crop is mature, and the rice is harvested 2 to 3 weeks later with large combines. In rice breeding programs, breeders try to employ the production systems predominant in their respective region. Thus, a drill-seeded breeding nursery is used by breeders in a region where rice is drill-seeded and a water-seeded nursery is used in regions where water-seeding is important.

Rice in the United States is classified into three primary market types by grain size, shape, and chemical composition of the endosperm: long-grain, medium grain and short-grain. Typical U. S. long-grain cultivars cook dry and fluffy when steamed or boiled, whereas medium- and short-grain cultivars cook moist and sticky. Long-grain cultivars have been traditionally grown in the southern states and generally receive higher market prices.

Rice, Oryza sativa L., is an important and valuable field crop. Thus, a continuing goal of plant breeders is to develop stable, high yielding rice cultivars that are agronomically sound. The reasons for this goal are obviously to maximize the amount of grain produced on the land used and to supply food for both animals and humans. To accomplish this goal, the rice breeder must select and develop rice plants that have the traits that result in superior cultivars.

The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.

SUMMARY OF THE INVENTION

The following embodiments and aspects thereof are described in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above described problems have been reduced or eliminated, while other embodiments are directed to other improvements.

According to the invention, there is provided a novel rice cultivar designated L-207. This invention thus relates to the seeds of rice cultivar L-207, to the plants of rice L-207 and to methods for producing a rice plant produced by crossing the rice L-207 with itself or another rice line.

Thus, any such methods using the rice variety L-207 are part of this invention: selfing, backcrosses, hybrid production, crosses to populations, and the like. All plants produced using rice variety L-207 as a parent are within the scope of this invention. Advantageously, the rice variety could be used in crosses with other, different, rice plants to produce first generation (F₁) rice hybrid seeds and plants with superior characteristics.

In another aspect, the present invention provides for single gene converted plants of L-207. The single transferred gene may preferably be a dominant or recessive allele. Preferably, the single transferred gene will confer such traits as herbicide resistance, insect resistance, resistance for bacterial, fungal, or viral disease, male fertility, male sterility, enhanced nutritional quality, and industrial usage. The single gene may be a naturally occurring rice gene or a transgene introduced through genetic engineering techniques.

In another aspect, the present invention provides regenerable cells for use in tissue culture of rice plant L-207. The tissue culture will preferably be capable of regenerating plants having the physiological and morphological characteristics of the foregoing rice plant, and of regenerating plants having substantially the same genotype as the foregoing rice plant. Preferably, the regenerable cells in such tissue cultures will be embryos, protoplasts, meristematic cells, callus, pollen, leaves, anthers, root tips, flowers, seeds, panicles or stems. Still further, the present invention provides rice plants regenerated from the tissue cultures of the invention.

In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by study of the following descriptions.

DETAILED DESCRIPTION OF THE INVENTION

In the description and tables which follow, a number of terms are used. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided:

Abiotic stress. As used herein, abiotic stress relates to all non-living chemical and physical factors in the environment. Examples of abiotic stress include, but are not limited to, drought, flooding, salinity, temperature, and climate change.

Aggregate sheath spot. Is caused by the fungus Rhizoctonia oryzae-sativae (Sawada) Mordue (=Ceratobasidium oryzae-sativae). This disease causes sheath lesions and can reduce yield and grain quality. California varieties generally rate between 2 and 4 in greenhouse tests on a scale of 0 to 4.

Alkali spreading value. Indicator of gelatinization temperature and an index that measures the extent of disintegration of milled rice kernel in contact with dilute alkali solution. Standard long grains have 3 to 5 Alkali Spreading Value (intermediate gelatinization temperature). Standard medium and short grain rice have 6 to 7 Alkali Spreading Values (low gelatinization temperature).

Allele. Allele is any of one or more alternative forms of a gene, all of which alleles relate to one trait or characteristic. In a diploid cell or organism, the two alleles of a given gene occupy corresponding loci on a pair of homologous chromosomes.

Alter. The utilization of up-regulation, down-regulation, or gene silencing.

Apparent amylose percent. The most important grain characteristic that describes cooking behavior in each grain class, or type, i.e., long, medium and short grain. The percentage of the endosperm starch of milled rice that is amylose. Standard long grains contain 20 to 23% amylose. Rexmont type long grains contain 24 to 25% amylose. Short and medium grain rice contain 16 to 19% amylose. Waxy rice contains 0% amylose. Amylose values will vary over environments.

Backcrossing. Backcrossing is a process in which a breeder repeatedly crosses hybrid progeny back to one of the parents, for example, a first generation hybrid F₁ with one of the parental genotypes of the F₁ hybrid.

Bakanae. Is caused by the fungus Fusarium fujikuroi Nirenberg (=Gibberella fujikuroi). It causes reduced seed germination and abnormal seedling elongation often followed by crown rot. Susceptibility of varieties is expressed as percent symptomatic plants.

Blanking %. Visual estimate of the percent of sterile florets (florets that are empty with no filled kernels) in the panicle as a measurement of cool temperature induced pollen sterility. Blanking may also be induced by high temperatures and by genetic incompatibility of the parents. This data may be collected in screening nurseries at cool locations, cool years, and also in screening tests in refrigerated greenhouses.

Breakdown. The peak viscosity minus the hot paste viscosity.

Breeding. The genetic manipulation of living organisms.

Cell. Cell as used herein includes a plant cell, whether isolated, in tissue culture or incorporated in a plant or plant part.

Cross-pollination. Fertilization by the union of two gametes from different plants.

Cool paste viscosity. Viscosity measure of rice flour/water slurry after being heated to 95EC and uniformly cooled to 50EC (American Association of Cereal Chemist). Values less than 200 for cool paste indicate softer cooking types of rice.

Days to 50% heading. Average number of days from planting to the day when 50% of all panicles are exerted at least partially through the leaf sheath. A measure of maturity.

Diploid. A cell or organism having two sets of chromosomes.

Elongation. Cooked kernel elongation is the ratio of the cooked kernel length divided by the uncooked kernel length. Extreme cooked kernel elongation is a unique feature of basmati type rice and an important quality criterion for that market type.

Embryo. The embryo is the small plant contained within a mature seed.

Essentially all the physiological and morphological characteristics. A plant having essentially all the physiological and morphological characteristics means a plant having the physiological and morphological characteristics of the cultivar, except for the characteristics derived from the converted gene.

F_(#). The “F” symbol denotes the filial generation, and the # is the generation number, such as F₁, F₂, F₃, etc.

Final viscosity. Viscosity at the end of the test or cold paste.

Gene. As used herein, “gene” refers to a unit of inheritance corresponding to DNA or RNA that code for a type of protein or for an RNA chain that has a function in the organism.

Gene silencing. The interruption or suppression of the expression of a gene at the level of transcription or translation.

Genotype. Refers to the genetic constitution of a cell or organism.

Grain length (L). Length of a rice grain is measured in millimeters.

Grain width (W). Width of a rice grain is measured in millimeters.

Grain yield. Grain yield is measured in pounds per acre and at 14.0% moisture. Grain yield of rice is determined by the number of panicles per unit area, the number of fertile florets per panicle, and grain weight per floret.

Haploid. A cell or organism having one set of the two sets of chromosomes in a diploid.

Harvest moisture. The percent of moisture of the grain when harvested.

Head rice. Unbroken kernels of milled rice.

Hot paste viscosity. Viscosity measure of rice flour/water slurry after being heated to 95EC. Lower values indicate softer and stickier cooking types of rice.

Length/Width (L/W) ratio. This ratio is determined by dividing the average length (L) by the average width (W).

Linkage. Refers to a phenomenon wherein alleles on the same chromosome tend to segregate together more often than expected by chance if their transmission was independent.

Linkage disequilibrium. Refers to a phenomenon wherein alleles tend to remain together in linkage groups when segregating from parents to offspring, with a greater frequency than expected from their individual frequencies.

Locus. A defined segment of DNA.

Lodging resistance (also called Straw strength). Lodging is measured as a subjective rating and is percentage of the plant stems leaning or fallen completely to the ground before harvest. Visual scoring where 0%=all plants standing to 100%=all plant in plot are laying flat on the soil surface. Lodged plants are difficult to harvest and reduce yield and grain quality.

Milling yield. Milling yield is the total amount of milled rice (whole and broken kernels) recovered after removal of hulls, bran, and germ by milling and head-rice yield, the total amount of whole kernels recovered after milling. Values are expressed as weight percentage of the original paddy or rough rice sample that was milled. For example, a milling yield of 65/70 is a sample of 100 grams of rough rice that produced 65 grams of head rice and 70 grams of total milled rice.

Nucleic acid. An acidic, chainlike biological macromolecule consisting of multiple repeat units of phosphoric acid, sugar and purine and pyrimidine bases.

Nutraceutical. Refers to a food or food product that provides health and or medical benefits, including the prevention and treatment of disease. Such products may range from isolated nutrients, dietary supplements and specific diets to genetically engineered foods, herbal products, and processed foods such as cereals, soups and beverages.

1000 Grain wt. The weight of 1000 rice grains as measured in grams. It can be for paddy, brown or milled rice.

Pedigree. Refers to the lineage or genealogical descent of a plant.

Pedigree distance. Relationship among generations based on their ancestral links as evidenced in pedigrees. May be measured by the distance of the pedigree from a given starting point in the ancestry.

Percent identity. Percent identity as used herein refers to the comparison of the homozygous alleles of two rice varieties. Percent identity is determined by comparing a statistically significant number of the homozygous alleles of two developed varieties. For example, a percent identity of 90% between rice variety 1 and rice variety 2 means that the two varieties have the same allele at 90% of their loci.

Percent similarity. Percent identity as used herein refers to the comparison of the homozygous alleles of two rice varieties. Percent identity is determined by comparing a statistically significant number of the homozygous alleles of two developed varieties. For example, a percent identity of 90% between rice variety 1 and rice variety 2 means that the two varieties have the same allele at 90% of their loci.

Peak viscosity. The maximum viscosity attained during heating when a standardized instrument-specific protocol is applied to a defined rice flour-water slurry.

Plant. As used herein, the term “plant” includes reference to an immature or mature whole plant, including a plant from which seed, grain, or anthers have been removed. Seed or embryo that will produce the plant is also considered to be the plant.

Plant height. Plant height measured in centimeters or inches is taken from soil surface to the tip of the extended panicle at harvest.

Plant parts. As used herein, the term “plant parts” (or a rice plant, or a part thereof) includes but is not limited to protoplasts, leaves, stems, roots, root tips, anthers, pistils, seed, grain, embryo, pollen, ovules, cotyledon, hypocotyl, pod, flower, shoot, tissue, petiole, cells, meristematic cells, and the like.

Progeny. As used herein, includes an F₁ rice plant produced from the cross of two rice plants where at least one plant includes rice cultivar L-207 and progeny further includes, but is not limited to, subsequent F₂, F₃, F₄, F₅, F₆, F₇, F₈, F₉, and F₁₀ generational crosses with the recurrent parental line.

Quantitative Trait Loci (QTL). Quantitative trait loci (QTL) refer to genetic loci that control to some degree numerically representable traits that are usually continuously distributed.

RVA viscosity. Rapid Visco Analyzer is a widely used laboratory instrument to examine paste viscosity, or thickening ability of milled rice during the cooking process.

RVU. The RVA scale is measured in RVUs. This is the native viscosity unit of the RVA. 1 RVU is equivalent to 12 CP. CP equals “centipoises” which equals unit of viscosity (kg s⁻¹ m⁻¹) and 1 kg s⁻¹ m⁻¹ equals 1000 centipoises.

Regeneration. Regeneration refers to the development of a plant from tissue culture.

Setback. Setback 1 is the final viscosity minus trough viscosity. Setback 2 is the final viscosity minus peak viscosity and is what is most commonly referred to for rice quality testing.

Single gene converted (Conversion). Single gene converted (conversion), also known as coisogenic plants, refers to plants which are developed by a plant breeding technique called backcrossing wherein essentially all of the desired morphological and physiological characteristics of a variety are recovered in addition to the single gene transferred into the variety via the backcrossing technique or via genetic engineering.

Stem rot. Is caused by the fungus Sclerotium oryzae Cattaneo (=Magnaporthe salvinii). It produces sheath and stem lesions that can reduce yield and grain quality. California varieties are generally rated between 4.5 and 7.5 on a scale of 0 to 10.

Texture score. A relative subjective score used by the breeder in evaluating cooked rice samples. A score of 4 being most sticky and a score of 2 being the least sticky.

Trough viscosity. The minimum viscosity after the peak, normally occurring when the sample starts to cool.

Rice cultivar L-207 is an early maturing, glabrous, long-grain selection from a cross made at the Rice Experiment Station (RES), Biggs, Calif. in 2006. It is the product of pedigree breeding and has the pedigree PI614958/02Y516//99Y529. Female parent (PI614958/02Y516) was an F₁ plant. PI614958 is an Indica type germplasm that was introduced from China in 1996, by USDA-ARS. 02Y516 is a high yielding intermediate height selection from RES. The male parent, 99Y529, is an early maturing selection with high grain and milling yield, developed at RES.

The experimental designation of rice cultivar L-207 was 12Y20. L-207 was selected and advanced using the pedigree breeding method. L-207 underwent nine years (13 generations) of selection and evaluation from the original cross until the production of its foundation seeds, and was evaluated for three years in statewide yield tests. L-207 was chosen from the 13^(th) filial generation.

Rice cultivar L-207 is a long-grain rice that can be classified as Gramineae, Oryza sativa L., and Tropical Japonica. It is a photoperiod insensitive, early maturing, intermediate height cultivar. The floret hull (lemma and palea) is awnless and the hulls and leaves are glabrous. Anthocyanin pigmentation occurs only in the apiculus. L-207 has a colorless, non-aromatic, and non-waxy endosperm.

Rice cultivar L-207 is most similar to rice cultivar L-206 (U.S. Pat. No. 7,579,531) and is distinguished from L-206 by having a taller plant height (15 cm), 4 more days to 50% heading, lower scores for cold induced blanking, improved scores for resistance to stem rot and aggregate sheath spot, and higher grain yields. The agronomic characteristics of L-207 are compared to L-206 and M-206 in Table 2. Seedling vigor of L-207 is slightly higher than L-206 and same as M-206. Days to 50% heading for L-207 is an average of 4 days later than both L-206 and M-206. Rice cultivar L-207 is 15 cm taller than L-206 and 3 cm taller than M-206. The lodging potential of L-207 is significantly lower than M-206, but not significantly different from L-206. Susceptibility to cold induced blanking (Greenhouse blanking score) for L-207 is similar to M-206 and lower than L-206. Stem rot resistance for L-207 was similar to M-206 but higher than L-206 (lower SR score). Aggregate Sheath spot resistance for L-207 was higher than both L-206 and M-206.

Rice cultivar L-207 is adapted to warmer areas of the California rice growing region. L-207 is being released to serve the California long-grain market and can be comingled with L-206 for rice processing and marketing purposes.

Rice cultivar L-207 has shown uniformity and stability as described in the following variety description information. It has been self-pollinated a sufficient number of generations with careful attention to uniformity of plant type. The line has been increased with continued observation for uniformity.

Rice cultivar L-207 has the following morphologic and other characteristics (based primarily on data collected in California).

TABLE 1 VARIETY DESCRIPTION INFORMATION Grain type: Long Days to maturity (50% heading): 85 Culm: Angle (degrees from perpendicular after flowering): Erect (less than 30°) Length (soil level to top of extended panicle on main stem): 102.0 cm Height class: Medium Internode color (after flowering): Green Strength (lodging resistance): Strong (no lodging) Flag leaf (at maturity): Length: 58.0 cm Width: N/A Pubescence: Glabrous Leaf angle (after heading): Erect Blade color (at heading): Green Basal leaf sheath color (at heading): Green Ligule: Length (from base of collar to the tip, at late vegetative stage): 17.0 mm Color (late vegetative stage): White Shape: Acute to acuminate Collar color (late vegetative stage): Pale green Auricle color (late vegetative stage): Pale green Panicle: Length: 23.6 cm Type: Intermediate Secondary branching: Light Exertion (near maturity): 100% Exerted Shattering (at maturity): Low (less than 5%) Threshability: Intermediate Grain (spikelet): Awns (after full heading): Absent Apiculus color (at maturity): Straw Apiculus color (after full heading): Purple Stigma color: White Lemma and palea color (at maturity): Straw Lemma and palea pubescence: Glabrous Spikelet sterility (at maturity): Fertile (75%-90%) Grain (seed): Seed coat color: Light brown Endosperm type: Non-glutinous (non-waxy) Endosperm translucency: Clear Endosperm chalkiness: None Scent: Non-scented Shape class (length/width ratio): Paddy: Long (3.4:1 and more) Length: 10.1 mm Width: 2.5 mm L/W ratio: 4.04 1000 Grains: 28.3 g Brown: Long (3.1:1 and more) Length: 7.9 mm Width: 2.2 mm L/W ratio: 3.59 1000 Grains: 22.1 g Milled: Long (3.0:1 and more) Length: 7.12 mm Width: 2.05 mm L/W ratio: 3.47 1000 Grains: 19.0 g Milling quality (% hulls): 20.8 Milling yield (% whole kernel (head) rice to rough rice): 65 % Protein (brown): 6.14 % Amylose: 23.8 Alkali spreading value: Gelatinization temperature type: Intermediate Amylographic paste viscosity (RVA measured in RVU): Peak: 251 Hot paste: 130 Cooled paste: 265 Setback: 14 Resistance to low temperature: Germination and seedling vigor: High Flowering (spikelet fertility): Low Seedling vigor not related to low temperature: Medium Disease resistance: Rice blast (Pyricularia oryzae): Susceptible to races in California Aggregate sheath spot (Rhizoctonia oryzae-sativae): Moderately susceptible Stem rot (Sclerotium oryzae): Moderately susceptible Insect resistance: Rice water weevil (Lissorhoptrus oryzophilus): Susceptible

This invention also is directed to methods for producing a rice plant by crossing a first parent rice plant with a second parent rice plant wherein either the first or second parent rice plant is a rice plant of the line L-207. Further, both first and second parent rice plants can come from the rice cultivar L-207. Still further, this invention also is directed to methods for producing a rice cultivar L-207-derived rice plant by crossing rice cultivar L-207 with a second rice plant and growing the progeny seed, and repeating the crossing and growing steps with the rice cultivar L-207-derived plant from 0 to 7 times. Thus, any such methods using the rice cultivar L-207 are part of this invention: selfing, backcrosses, hybrid production, crosses to populations, and the like. All plants produced using rice cultivar L-207 as a parent are within the scope of this invention, including plants derived from rice cultivar L-207. Advantageously, the rice cultivar is used in crosses with other, different, rice cultivars to produce first generation (F₁) rice seeds and plants with superior characteristics.

It should be understood that the cultivar can, through routine manipulation of cytoplasmic or other factors, be produced in a male-sterile form. Such embodiments are also contemplated within the scope of the present claims.

As used herein, the term plant includes plant cells, plant protoplasts, plant cell tissue cultures from which rice plants can be regenerated, plant calli, plant clumps and plant cells that are intact in plants or parts of plants, such as embryos, pollen, ovules, flowers, glumes, panicles, leaves, stems, roots, root tips, anthers, pistils and the like.

Further Embodiments of the Invention

With the advent of molecular biological techniques that have allowed the isolation and characterization of genes that encode specific protein products, scientists in the field of plant biology developed a strong interest in engineering the genome of plants to contain and express foreign genes, or additional, or modified versions of native, or endogenous, genes (perhaps driven by different promoters) in order to alter the traits of a plant in a specific manner. Such foreign additional and/or modified genes are referred to herein collectively as “transgenes”. Over the last fifteen to twenty years, several methods for producing transgenic plants have been developed, and the present invention, in particular embodiments, also relates to transformed versions of the claimed cultivar.

Culture for expressing desired structural genes and cultured cells are known in the art. Also as known in the art, rice is transformable and regenerable such that whole plants containing and expressing desired genes under regulatory control may be obtained. General descriptions of plant expression vectors and reporter genes and transformation protocols can be found in Gruber, et al., “Vectors for Plant Transformation”, in Methods in Plant Molecular Biology & Biotechnology in Glich, et al., (Eds. pp. 89-119, CRC Press, 1993). Moreover GUS expression vectors and GUS gene cassettes are available from Clone Tech Laboratories, Inc., Palo Alto, Calif. while luciferase expression vectors and luciferase gene cassettes are available from Pro Mega Corp. (Madison, Wis.). General methods of culturing plant tissues are provided for example by Maki, et al., “Procedures for Introducing Foreign DNA into Plants” in Methods in Plant Molecular Biology & Biotechnology, Glich, et al., (Eds. pp. 67-88 CRC Press, 1993); and by Phillips, et al., “Cell-Tissue Culture and In-Vitro Manipulation” in Corn & Corn Improvement, 3rd Edition; Sprague, et al., (Eds. pp. 345-387 American Society of Agronomy Inc., 1988). Methods of introducing expression vectors into plant tissue include the direct infection or co-cultivation of plant cells with Agrobacterium tumefaciens, described for example by Horsch et al., Science, 227:1229 (1985). Descriptions of Agrobacterium vector systems and methods for Agrobacterium-mediated gene transfer are provided by Gruber, et al., supra.

Useful methods include but are not limited to expression vectors introduced into plant tissues using a direct gene transfer method such as microprojectile-mediated delivery, DNA injection, electroporation and the like. More preferably expression vectors are introduced into plant tissues using a microprojectile media delivery system with a biolistic device or using Agrobacterium-mediated transformation. Transformant plants obtained with the protoplasm of the invention are intended to be within the scope of this invention.

Plant transformation involves the construction of an expression vector which will function in plant cells. Such a vector comprises DNA comprising a gene under control of or operatively linked to a regulatory element (for example, a promoter). The expression vector may contain one or more such operably linked gene/regulatory element combinations. The vector(s) may be in the form of a plasmid, and can be used alone or in combination with other plasmids, to provide transformed rice plants, using transformation methods as described below to incorporate transgenes into the genetic material of the rice plant(s).

Expression Vectors for Transformation: Marker Genes

Expression vectors include at least one genetic marker, operably linked to a regulatory element (a promoter, for example) that allows transformed cells containing the marker to be either recovered by negative selection, i.e., inhibiting growth of cells that do not contain the selectable marker gene, or by positive selection, i.e., screening for the product encoded by the genetic marker. Many commonly used selectable marker genes for plant transformation are well known in the transformation arts, and include, for example, genes that code for enzymes that metabolically detoxify a selective chemical agent which may be an antibiotic or an herbicide, or genes that encode an altered target which is insensitive to the inhibitor. A few positive selection methods are also known in the art.

One commonly used selectable marker gene for plant transformation is the neomycin phosphotransferase II (nptII) gene, isolated from transposon Tn5, which when placed under the control of plant regulatory signals confers resistance to kanamycin. Fraley et al., Proc. Natl. Acad. Sci. U.S.A., 80:4803 (1983). Another commonly used selectable marker gene is the hygromycin phosphotransferase gene which confers resistance to the antibiotic hygromycin. Vanden Elzen et al., Plant Mol. Biol., 5:299 (1985).

Selectable marker genes for plant transformation not of bacterial origin include, for example, mouse dihydrofolate reductase, plant 5-enolpyruvylshikimate-3-phosphate synthase and plant acetolactate synthase. Eichholtz et al., Somatic Cell Mol. Genet. 13:67 (1987), Shah et al., Science 233:478 (1986), Charest et al., Plant Cell Rep. 8:643 (1990).

Additional selectable marker genes of bacterial origin that confer resistance to antibiotics include gentamycin acetyl transferase, streptomycin phosphotransferase, and aminoglycoside-3′-adenyl transferase, the bleomycin resistance determinant. Hayford et al., Plant Physiol. 86:1216 (1988); Jones et al., Mol. Gen. Genet., 210:86 (1987); Svab et al., Plant Mol. Biol. 14:197 (1990); Hille et al., Plant Mol. Biol. 7:171 (1986). Other selectable marker genes confer resistance to herbicides such as glyphosate, glufosinate or bromoxynil. Comai et al., Nature 317:741-744 (1985), Gordon-Kamm et al., Plant Cell 2:603-618 (1990) and Stalker et al., Science 242:419-423 (1988).

Another class of marker genes for plant transformation requires screening of presumptively transformed plant cells rather than direct genetic selection of transformed cells for resistance to a toxic substance such as an antibiotic. These genes are particularly useful to quantify or visualize the spatial pattern of expression of a gene in specific tissues and are frequently referred to as reporter genes because they can be fused to a gene or gene regulatory sequence for the investigation of gene expression. Commonly used genes for screening presumptively transformed cells include β-glucuronidase (GUS, β-galactosidase, luciferase and chloramphenicol acetyltransferase. Jefferson, R. A., Plant Mol. Biol. Rep. 5:387 (1987), Teeri et al., EMBO J. 8:343 (1989), Koncz et al., Proc. Natl. Acad. Sci U.S.A. 84:131 (1987), DeBlock et al., EMBO J. 3:1681 (1984). Another approach to the identification of relatively rare transformation events has been use of a gene that encodes a dominant constitutive regulator of the Zea mays anthocyanin pigmentation pathway. Ludwig et al., Science 247:449 (1990).

In vivo methods for visualizing GUS activity that do not require destruction of plant tissue are available. Molecular Probes publication 2908, IMAGENE GREEN, p. 1-4 (1993) and Naleway et al., J. Cell Biol. 115:151a (1991). However, these in vivo methods for visualizing GUS activity have not proven useful for recovery of transformed cells because of low sensitivity, high fluorescent backgrounds and limitations associated with the use of luciferase genes as selectable markers.

More recently, a gene encoding Green Fluorescent Protein (GFP) has been utilized as a marker for gene expression in prokaryotic and eukaryotic cells. Chalfie et al., Science 263:802 (1994). GFP and mutants of GFP may be used as screenable markers.

Expression Vectors for Transformation: Promoters

Genes included in expression vectors must be driven by nucleotide sequence comprising a regulatory element, for example, a promoter. Several types of promoters are now well known in the transformation arts, as are other regulatory elements that can be used alone or in combination with promoters.

As used herein, “promoter” includes reference to a region of DNA upstream from the start of transcription and involved in recognition and binding of RNA polymerase and other proteins to initiate transcription. A “plant promoter” is a promoter capable of initiating transcription in plant cells. Examples of promoters under developmental control include promoters that preferentially initiate transcription in certain tissues, such as leaves, roots, seeds, fibers, xylem vessels, tracheids, or sclerenchyma. Such promoters are referred to as “tissue-preferred”. Promoters which initiate transcription only in certain tissue are referred to as “tissue-specific”. A “cell type” specific promoter primarily drives expression in certain cell types in one or more organs, for example, vascular cells in roots or leaves. An “inducible” promoter is a promoter which is under environmental control. Examples of environmental conditions that may effect transcription by inducible promoters include anaerobic conditions or the presence of light. Tissue-specific, tissue-preferred, cell type specific, and inducible promoters constitute the class of “non-constitutive” promoters. A “constitutive” promoter is a promoter which is active under most environmental conditions.

A. Inducible Promoters—An inducible promoter is operably linked to a gene for expression in rice. Optionally, the inducible promoter is operably linked to a nucleotide sequence encoding a signal sequence which is operably linked to a gene for expression in rice. With an inducible promoter the rate of transcription increases in response to an inducing agent.

Any inducible promoter can be used in the instant invention. See Ward et al., Plant Mol. Biol. 22:361-366 (1993). Exemplary inducible promoters include, but are not limited to, that from the ACEI system which responds to copper (Meft et al., PNAS 90:4567-4571 (1993)); In2 gene from maize which responds to benzenesulfonamide herbicide safeners (Hershey et al., Mol. Gen Genetics 227:229-237 (1991) and Gatz et al., Mol. Gen. Genetics 243:32-38 (1994)) or Tet repressor from Tn10 (Gatz et al., Mol. Gen. Genetics 227:229-237 (1991)). A particularly preferred inducible promoter is a promoter that responds to an inducing agent to which plants do not normally respond. An exemplary inducible promoter is the inducible promoter from a steroid hormone gene, the transcriptional activity of which is induced by a glucocorticosteroid hormone (Schena et al., Proc. Natl. Acad. Sci. U.S.A. 88:0421 (1991)).

B. Constitutive Promoters—A constitutive promoter is operably linked to a gene for expression in rice or the constitutive promoter is operably linked to a nucleotide sequence encoding a signal sequence which is operably linked to a gene for expression in rice.

Many different constitutive promoters can be utilized in the instant invention. Exemplary constitutive promoters include, but are not limited to, the promoters from plant viruses such as the 35S promoter from CaMV (Odell et al., Nature 313:810-812 (1985)) and the promoters from such genes as rice actin (McElroy et al., Plant Cell 2:163-171 (1990)); ubiquitin (Christensen et al., Plant Mol. Biol. 12:619-632 (1989) and Christensen et al., Plant Mol. Biol. 18:675-689 (1992)); pEMU (Last et al., Theor. Appl. Genet. 81:581-588 (1991)); MAS (Velten et al., EMBO J. 3:2723-2730 (1984)) and maize H3 histone (Lepetit et al., Mol. Gen. Genetics 231:276-285 (1992) and Atanassova et al., Plant Journal 2 (3): 291-300 (1992)).

The ALS promoter, Xba1/Nco1 fragment 5′ to the Brassica napus ALS3 structural gene (or a nucleotide sequence similarity to said Xba1/Nco1 fragment), represents a particularly useful constitutive promoter. See PCT application WO96/30530.

C. Tissue-specific or Tissue-preferred Promoters—A tissue-specific promoter is operably linked to a gene for expression in rice. Optionally, the tissue-specific promoter is operably linked to a nucleotide sequence encoding a signal sequence which is operably linked to a gene for expression in rice. Plants transformed with a gene of interest operably linked to a tissue-specific promoter produce the protein product of the transgene exclusively, or preferentially, in a specific tissue.

Any tissue-specific or tissue-preferred promoter can be utilized in the instant invention. Exemplary tissue-specific or tissue-preferred promoters include, but are not limited to, a root-preferred promoter, such as that from the phaseolin gene (Murai et al., Science 23:476-482 (1983) and Sengupta-Gopalan et al., Proc. Natl. Acad. Sci. U.S.A. 82:3320-3324 (1985)); a leaf-specific and light-induced promoter such as that from cab or rubisco (Simpson et al., EMBO J. 4(11):2723-2729 (1985) and Timko et al., Nature 318:579-582 (1985)); an anther-specific promoter such as that from LAT52 (Twell et al., Mol. Gen. Genetics 217:240-245 (1989)); a pollen-specific promoter such as that from Zm13 (Guerrero et al., Mol. Gen. Genetics 244:161-168 (1993)) or a microspore-preferred promoter such as that from apg (Twell et al., Sex. Plant Reprod. 6:217-224 (1993)).

Signal Sequences for Targeting Proteins to Subcellular Compartments

Transport of protein produced by transgenes to a subcellular compartment such as the chloroplast, vacuole, peroxisome, glyoxysome, cell wall or mitochondrion or for secretion into the apoplast, is accomplished by means of operably linking the nucleotide sequence encoding a signal sequence to the 5′ and/or 3′ region of a gene encoding the protein of interest. Targeting sequences at the 5′ and/or 3′ end of the structural gene may determine, during protein synthesis and processing, where the encoded protein is ultimately compartmentalized.

The presence of a signal sequence directs a polypeptide to either an intracellular organelle or subcellular compartment or for secretion to the apoplast. Many signal sequences are known in the art. See, for example Becker et al., Plant Mol. Biol. 20:49 (1992); Close, P. S., Master's Thesis, Iowa State University (1993); Knox, C., et al., Plant Mol. Biol. 9:3-17 (1987); Lerner et al., Plant Physiol. 91:124-129 (1989); Fontes et al., Plant Cell 3:483-496 (1991); Matsuoka et al., Proc. Natl. Acad. Sci. 88:834 (1991); Gould et al., J. Cell. Biol. 108:1657 (1989); Creissen et al., Plant 2:129 (1991); Kalderon, et al., Cell 39:499-509 (1984); Steifel, et al., Plant Cell 2:785-793 (1990).

Foreign Protein Genes and Agronomic Genes

With transgenic plants according to the present invention, a foreign protein can be produced in commercial quantities. Thus, techniques for the selection and propagation of transformed plants, which are well understood in the art, yield a plurality of transgenic plants which are harvested in a conventional manner, and a foreign protein then can be extracted from a tissue of interest or from total biomass. Protein extraction from plant biomass can be accomplished by known methods which are discussed, for example, by Heney and Orr, Anal. Biochem. 114:92-6 (1981).

According to a preferred embodiment, the transgenic plant provided for commercial production of foreign protein is rice. In another preferred embodiment, the biomass of interest is seed. For the relatively small number of transgenic plants that show higher levels of expression, a genetic map can be generated, primarily via conventional RFLP, PCR and SSR analysis, which identifies the approximate chromosomal location of the integrated DNA molecule. For exemplary methodologies in this regard, see Glick and Thompson, Methods in Plant Molecular Biology and Biotechnology CRC Press, Boca Raton 269:284 (1993). Map information concerning chromosomal location is useful for proprietary protection of a subject transgenic plant. If unauthorized propagation is undertaken and crosses made with other germplasm, the map of the integration region can be compared to similar maps for suspect plants, to determine if the latter have a common parentage with the subject plant. Map comparisons would involve hybridizations, RFLP, PCR, SSR and sequencing, all of which are conventional techniques.

Likewise, by means of the present invention, agronomic genes can be expressed in transformed plants. More particularly, plants can be genetically engineered to express various phenotypes of agronomic interest. Exemplary genes implicated in this regard include, but are not limited to, those categorized below:

1. Genes that Confer Resistance to Pests or Disease and that Encode:

A. Plant disease resistance genes. Plant defenses are often activated by specific interaction between the product of a disease resistance gene (R) in the plant and the product of a corresponding avirulence (Avr) gene in the pathogen. A plant cultivar can be transformed with cloned resistance gene to engineer plants that are resistant to specific pathogen strains. See, for example Jones et al., Science 266:789 (1994) (cloning of the tomato Cf-9 gene for resistance to Cladosporium fulvum); Martin et al., Science 262:1432 (1993) (tomato Pto gene for resistance to Pseudomonas syringae pv. tomato encodes a protein kinase); Mindrinos et al., Cell 78:1089 (1994) (Arabidopsis RSP2 gene for resistance to Pseudomonas syringae).

B. A Bacillus thuringiensis protein, a derivative thereof or a synthetic polypeptide modeled thereon. See, for example, Geiser et al., Gene 48:109 (1986), who disclose the cloning and nucleotide sequence of a Bt δ-endotoxin gene. Moreover, DNA molecules encoding 6-endotoxin genes can be purchased from American Type Culture Collection, Manassas, Va., for example, under ATCC Accession Nos. 40098, 67136, 31995 and 31998.

C. A lectin. See, for example, the disclosure by Van Damme et al., Plant Molec. Biol. 24:25 (1994), who disclose the nucleotide sequences of several Clivia miniata mannose-binding lectin genes.

D. A vitamin-binding protein such as avidin. See PCT application US93/06487. The application teaches the use of avidin and avidin homologues as larvicides against insect pests.

E. An enzyme inhibitor, for example, a protease or proteinase inhibitor or an amylase inhibitor. See, for example, Abe et al., J. Biol. Chem. 262:16793 (1987) (nucleotide sequence of rice cysteine proteinase inhibitor), Huub et al., Plant Molec. Biol. 21:985 (1993) (nucleotide sequence of cDNA encoding tobacco proteinase inhibitor I), Sumitani et al., Biosci. Biotech. Biochem. 57:1243 (1993) (nucleotide sequence of Streptomyces nitrosporeus α-amylase inhibitor).

F. An insect-specific hormone or pheromone such as an ecdysteroid and juvenile hormone, a variant thereof, a mimetic based thereon, or an antagonist or agonist thereof. See, for example, the disclosure by Hammock et al., Nature 344:458 (1990), of baculovirus expression of cloned juvenile hormone esterase, an inactivator of juvenile hormone.

G. An insect-specific peptide or neuropeptide which, upon expression, disrupts the physiology of the affected pest. For example, see the disclosures of Regan, J. Biol. Chem. 269:9 (1994) (expression cloning yields DNA coding for insect diuretic hormone receptor), and Pratt et al., Biochem. Biophys. Res. Comm. 163:1243 (1989) (an allostatin is identified in Diploptera puntata). See also U.S. Pat. No. 5,266,317 to Tomalski et al., who disclose genes encoding insect-specific, paralytic neurotoxins.

H. An insect-specific venom produced in nature by a snake, a wasp, etc. For example, see Pang et al., Gene 116:165 (1992), for disclosure of heterologous expression in plants of a gene coding for a scorpion insectotoxic peptide.

I. An enzyme responsible for a hyper-accumulation of a monoterpene, a sesquiterpene, a steroid, a hydroxamic acid, a phenylpropanoid derivative or another non-protein molecule with insecticidal activity.

J. An enzyme involved in the modification, including the post-translational modification, of a biologically active molecule; for example, a glycolytic enzyme, a proteolytic enzyme, a lipolytic enzyme, a nuclease, a cyclase, a transaminase, an esterase, a hydrolase, a phosphatase, a kinase, a phosphorylase, a polymerase, an elastase, a chitinase and a glucanase, whether natural or synthetic. See PCT application WO 93/02197 in the name of Scott et al., which discloses the nucleotide sequence of a callase gene. DNA molecules which contain chitinase-encoding sequences can be obtained, for example, from the ATCC under Accession Nos. 39637 and 67152. See also Kramer et al., Insect Biochem. Molec. Biol. 23:691 (1993), who teach the nucleotide sequence of a cDNA encoding tobacco hornworm chitinase, and Kawalleck et al., Plant Molec. Biol. 21:673 (1993), who provide the nucleotide sequence of the parsley ubi4-2 polyubiquitin gene.

K. A molecule that stimulates signal transduction. For example, see the disclosure by Botella et al., Plant Molec. Biol. 24:757 (1994), of nucleotide sequences for mung bean calmodulin cDNA clones, and Griess et al., Plant Physiol. 104:1467 (1994), who provide the nucleotide sequence of a maize calmodulin cDNA clone.

L. A hydrophobic moment peptide. See PCT application WO95/16776 (disclosure of peptide derivatives of Tachyplesin which inhibit fungal plant pathogens) and PCT application WO95/18855 (teaches synthetic antimicrobial peptides that confer disease resistance), the respective contents of which are hereby incorporated by reference.

M. A membrane permease, a channel former or a channel blocker. For example, see the disclosure of Jaynes et al., Plant Sci 89:43 (1993), of heterologous expression of a cecropin-β, lytic peptide analog to render transgenic tobacco plants resistant to Pseudomonas solanacearum.

N. A viral-invasive protein or a complex toxin derived therefrom. For example, the accumulation of viral coat proteins in transformed plant cells imparts resistance to viral infection and/or disease development effected by the virus from which the coat protein gene is derived, as well as by related viruses. See Beachy et al., Ann. Rev. Phytopathol. 28:451 (1990). Coat protein-mediated resistance has been conferred upon transformed plants against alfalfa mosaic virus, cucumber mosaic virus, tobacco streak virus, potato virus X, potato virus Y, tobacco etch virus, tobacco rattle virus and tobacco mosaic virus. Id.

O. An insect-specific antibody or an immunotoxin derived therefrom. Thus, an antibody targeted to a critical metabolic function in the insect gut would inactivate an affected enzyme, killing the insect. Cf. Taylor et al., Abstract #497, Seventh Int'l Symposium on Molecular Plant-Microbe Interactions (Edinburgh, Scotland) (1994) (enzymatic inactivation in transgenic tobacco via production of single-chain antibody fragments).

P. A virus-specific antibody. See, for example, Tavladoraki et al., Nature 366:469 (1993), who show that transgenic plants expressing recombinant antibody genes are protected from virus attack.

Q. A developmental-arrestive protein produced in nature by a pathogen or a parasite. Thus, fungal endo-α-1, 4-D-polygalacturonases facilitate fungal colonization and plant nutrient release by solubilizing plant cell wall homo-α-1,4-D-galacturonase. See Lamb et al., Bio/Technology 10:1436 (1992). The cloning and characterization of a gene which encodes a bean endopolygalacturonase-inhibiting protein is described by Toubart et al., Plant J. 2:367 (1992).

R. A developmental-arrestive protein produced in nature by a plant. For example, Logemann et al., Bio/Technology 10:305 (1992), have shown that transgenic plants expressing the barley ribosome-inactivating gene have an increased resistance to fungal disease.

2. Genes that Confer Resistance to an Herbicide, for Example:

A. An herbicide that inhibits the growing point or meristem, such as an imidazolinone or a sulfonylurea. Exemplary genes in this category code for mutant ALS and AHAS enzyme as described, for example, by Lee et al., EMBO J. 7:1241 (1988), and Miki et al., Theor. Appl. Genet. 80:449 (1990), respectively.

B. Glyphosate (resistance conferred by mutant 5-enolpyruvlshikimate-3-phosphate synthase (EPSP) and aroA genes, respectively) and other phosphono compounds such as glufosinate (phosphinothricin acetyl transferase (PAT) and Streptomyces hygroscopicus PAT, bar, genes), and pyridinoxy or phenoxy propionic acids and cyclohexones (ACCase inhibitor-encoding genes). See, for example, U.S. Pat. No. 4,940,835 to Shah, et al., which discloses the nucleotide sequence of a form of EPSP which can confer glyphosate resistance. A DNA molecule encoding a mutant aroA gene can be obtained under ATCC accession number 39256, and the nucleotide sequence of the mutant gene is disclosed in U.S. Pat. No. 4,769,061 to Comai. European patent application No. 0 333 033 to Kumada et al., and U.S. Pat. No. 4,975,374 to Goodman et al., disclose nucleotide sequences of glutamine synthetase genes which confer resistance to herbicides such as L-phosphinothricin. The nucleotide sequence of a PAT gene is provided in European application No. 0 242 246 to Leemans et al. DeGreef et al., Bio/Technology 7:61 (1989), describe the production of transgenic plants that express chimeric bar genes coding for PAT activity. Exemplary of genes conferring resistance to phenoxy propionic acids and cyclohexones, such as sethoxydim and haloxyfop are the Acc1-S1, Acc1-S2 and Acc1-S3 genes described by Marshall et al., Theor. Appl. Genet. 83:435 (1992).

C. An herbicide that inhibits photosynthesis, such as a triazine (psbA and gs+ genes) or a benzonitrile (nitrilase gene). Przibilla et al., Plant Cell 3:169 (1991), describe the transformation of Chlamydomonas with plasmids encoding mutant psbA genes. Nucleotide sequences for nitrilase genes are disclosed in U.S. Pat. No. 4,810,648 to Stalker, and DNA molecules containing these genes are available under ATCC Accession Nos. 53435, 67441, and 67442. Cloning and expression of DNA coding for a glutathione S-transferase is described by Hayes et al., Biochem. J. 285:173 (1992).

3. Genes that Confer or Contribute to a Value-Added Trait, Such as:

A. Modified fatty acid metabolism, for example, by transforming a plant with an antisense gene of stearyl-ACP desaturase to increase stearic acid content of the plant. See Knultzon et al., Proc. Natl. Acad. Sci. U.S.A. 89:2624 (1992).

B. Decreased phytate content, 1) Introduction of a phytase-encoding gene would enhance breakdown of phytate, adding more free phosphate to the transformed plant. For example, see Van Hartingsveldt et al., Gene 127:87 (1993), for a disclosure of the nucleotide sequence of an Aspergillus niger phytase gene; 2) A gene could be introduced that reduced phytate content. In maize, this, for example, could be accomplished, by cloning and then reintroducing DNA associated with the single allele which is responsible for maize mutants characterized by low levels of phytic acid. See Raboy et al., Maydica 35:383 (1990).

C. Modified carbohydrate composition effected, for example, by transforming plants with a gene coding for an enzyme that alters the branching pattern of starch. See Shiroza et al., J. Bacteol. 170:810 (1988) (nucleotide sequence of Streptococcus mutants fructosyltransferase gene), Steinmetz et al., Mol. Gen. Genet. 20:220 (1985) (nucleotide sequence of Bacillus subtilis levansucrase gene), Pen et al., Bio/Technology 10:292 (1992) (production of transgenic plants that express Bacillus lichenifonnis α-amylase), Elliot et al., Plant Molec. Biol. 21:515 (1993) (nucleotide sequences of tomato invertase genes), Søgaard et al., J. Biol. Chem. 268:22480 (1993) (site-directed mutagenesis of barley α-amylase gene), and Fisher et al., Plant Physiol. 102:1045 (1993) (maize endosperm starch branching enzyme II).

Methods for Transformation

Numerous methods for plant transformation have been developed, including biological and physical, plant transformation protocols. See, for example, Miki et al., “Procedures for Introducing Foreign DNA into Plants” in Methods in Plant Molecular Biology and Biotechnology, Glick B. R. and Thompson, J. E. Eds. (CRC Press, Inc., Boca Raton, 1993) pages 67-88. In addition, expression vectors and in vitro culture methods for plant cell or tissue transformation and regeneration of plants are available. See, for example, Gruber et al., “Vectors for Plant Transformation” in Methods in Plant Molecular Biology and Biotechnology, Glick B. R. and Thompson, J. E. Eds. (CRC Press, Inc., Boca Raton, 1993) pages 89-119.

A. Agrobacterium-mediated Transformation—One method for introducing an expression vector into plants is based on the natural transformation system of Agrobacterium. See, for example, Horsch et al., Science 227:1229 (1985). A. tumefaciens and A. rhizogenes are plant pathogenic soil bacteria which genetically transform plant cells. The Ti and Ri plasmids of A. tumefaciens and A. rhizogenes, respectively, carry genes responsible for genetic transformation of the plant. See, for example, Kado, C. I., Crit. Rev. Plant Sci. 10:1 (1991). Descriptions of Agrobacterium vector systems and methods for Agrobacterium-mediated gene transfer are provided by Gruber et al., supra, Miki et al., supra, and Moloney et al., Plant Cell Reports 8:238 (1989). See also, U.S. Pat. No. 5,591,616 issued Jan. 7, 1997.

B. Direct Gene Transfer—Despite the fact the host range for Agrobacterium-mediated transformation is broad, some major cereal crop species and gymnosperms have generally been recalcitrant to this mode of gene transfer, even though some success has recently been achieved in rice and corn. Hiei et al., The Plant Journal 6:271-282 (1994) and U.S. Pat. No. 5,591,616 issued Jan. 7, 1997. Several methods of plant transformation collectively referred to as direct gene transfer, have been developed as an alternative to Agrobacterium-mediated transformation.

A generally applicable method of plant transformation is microprojectile-mediated transformation wherein DNA is carried on the surface of microprojectiles measuring 1 to 4 μm. The expression vector is introduced into plant tissues with a biolistic device that accelerates the microprojectiles to speeds of 300 to 600 m/s which is sufficient to penetrate plant cell walls and membranes. Sanford et al., Part. Sci. Technol. 5:27 (1987), Sanford, J. C., Trends Biotech. 6:299 (1988), Klein et al., Bio/Technology 6:559-563 (1988), Sanford, J. C., Physiol Plant 7:206 (1990), Klein et al., Biotechnology 10:268 (1992). In corn, several target tissues can be bombarded with DNA-coated microprojectiles in order to produce transgenic plants, including, for example, callus (Type I or Type II), immature embryos, and meristematic tissue.

Another method for physical delivery of DNA to plants is sonication of target cells. Zhang et al., Bio/Technology 9:996 (1991). Additionally, liposome and spheroplast fusion have been used to introduce expression vectors into plants. Deshayes et al., EMBO J., 4:2731 (1985), Christou et al., Proc Natl. Acad. Sci. U.S.A. 84:3962 (1987). Direct uptake of DNA into protoplasts using CaCl₂ precipitation, polyvinyl alcohol or poly-L-ornithine has also been reported. Hain et al., Mol. Gen. Genet. 199:161 (1985) and Draper et al., Plant Cell Physiol. 23:451 (1982). Electroporation of protoplasts and whole cells and tissues have also been described. Donn et al., In Abstracts of VIIth International Congress on Plant Cell and Tissue Culture IAPTC, A2-38, p 53 (1990); D'Halluin et al., Plant Cell 4:1495-1505 (1992) and Spencer et al., Plant Mol. Biol. 24:51-61 (1994).

Following transformation of rice target tissues, expression of the above-described selectable marker genes allows for preferential selection of transformed cells, tissues and/or plants, using regeneration and selection methods now well known in the art.

The foregoing methods for transformation would typically be used for producing a transgenic cultivar. The transgenic cultivar could then be crossed, with another (non-transformed or transformed) cultivar, in order to produce a new transgenic cultivar. Alternatively, a genetic trait which has been engineered into a particular rice cultivar using the foregoing transformation techniques could be moved into another cultivar using traditional backcrossing techniques that are well known in the plant breeding arts. For example, a backcrossing approach could be used to move an engineered trait from a public, non-elite cultivar into an elite cultivar, or from a cultivar containing a foreign gene in its genome into a cultivar which does not contain that gene. As used herein, “crossing” can refer to a simple X by Y cross, or the process of backcrossing, depending on the context.

Single Gene Conversion

When the term rice plant is used in the context of the present invention, this also includes any single gene conversions of that cultivar. The term single gene converted plant as used herein refers to those rice plants which are developed by a plant breeding technique called backcrossing wherein essentially all of the desired morphological and physiological characteristics of a cultivar are recovered in addition to the single gene transferred into the cultivar via the backcrossing technique. Backcrossing methods can be used with the present invention to improve or introduce a characteristic into the cultivar. The term backcrossing as used herein refers to the repeated crossing of a hybrid progeny back to one of the parental rice plants, the recurrent parent, for that cultivar, i.e., backcrossing 1, 2, 3, 4, 5, 6, 7, 8, 9 or more times to the recurrent parent. The parental rice plant which contributes the gene for the desired characteristic is termed the nonrecurrent or donor parent. This terminology refers to the fact that the nonrecurrent parent is used one time in the backcross protocol and therefore does not recur. The parental rice plant to which the gene or genes from the nonrecurrent parent are transferred is known as the recurrent parent as it is used for several rounds in the backcrossing protocol (Poehlman & Sleper, 1994; Fehr, 1987). In a typical backcross protocol, the original cultivar of interest (recurrent parent) is crossed to a second cultivar (nonrecurrent parent) that carries the single gene of interest to be transferred. The resulting progeny from this cross are then crossed again to the recurrent parent and the process is repeated until a rice plant is obtained wherein essentially all of the desired morphological and physiological characteristics of the recurrent parent are recovered in the converted plant, in addition to the single transferred gene from the nonrecurrent parent as determined at the 5% significance level when grown in the same environmental conditions.

The selection of a suitable recurrent parent is an important step for a successful backcrossing procedure. The goal of a backcross protocol is to alter or substitute a single trait or characteristic in the original cultivar. To accomplish this, a single gene of the recurrent cultivar is modified or substituted with the desired gene from the nonrecurrent parent, while retaining essentially all of the rest of the desired genetic, and therefore the desired physiological and morphological, constitution of the original cultivar. The choice of the particular nonrecurrent parent will depend on the purpose of the backcross; one of the major purposes is to add some commercially desirable, agronomically important trait to the plant. The exact backcrossing protocol will depend on the characteristic or trait being altered to determine an appropriate testing protocol. Although backcrossing methods are simplified when the characteristic being transferred is a dominant allele, a recessive allele may also be transferred. In this instance it may be necessary to introduce a test of the progeny to determine if the desired characteristic has been successfully transferred.

Many single gene traits have been identified that are not regularly selected for in the development of a new cultivar but that can be improved by backcrossing techniques. Single gene traits may or may not be transgenic, examples of these traits include but are not limited to, male sterility, waxy starch, herbicide resistance, resistance for bacterial, fungal, or viral disease, insect resistance, male fertility, enhanced nutritional quality, industrial usage, yield stability and yield enhancement. These genes are generally inherited through the nucleus. Some known exceptions to this are the genes for male sterility, some of which are inherited cytoplasmically, but still act as single gene traits. Several of these single gene traits are described in U.S. Pat. Nos. 5,777,196; 5,948,957 and 5,969,212, the disclosures of which are specifically hereby incorporated by reference.

Tissue Culture

Further reproduction of the variety can occur by tissue culture and regeneration. Tissue culture of various tissues of rice and regeneration of plants therefrom is well known and widely published. For example, reference may be had to Komatsuda, T. et al., Crop Sci. 31:333-337 (1991); Stephens, P. A., et al., Theor. Appl. Genet. (1991) 82:633-635; Komatsuda, T. et al., Plant Cell, Tissue and Organ Culture, 28:103-113 (1992); Dhir, S. et al., Plant Cell Reports (1992) 11:285-289; Pandey, P. et al., Japan J. Breed. 42:1-5 (1992); and Shetty, K., et al., Plant Science 81:245-251 (1992); as well as U.S. Pat. No. 5,024,944 issued Jun. 18, 1991 to Collins et al., and U.S. Pat. No. 5,008,200 issued Apr. 16, 1991 to Ranch et al. Thus, another aspect of this invention is to provide cells which upon growth and differentiation produce rice plants having the physiological and morphological characteristics of rice variety L-207.

As used herein, the term “tissue culture” indicates a composition comprising isolated cells of the same or a different type or a collection of such cells organized into parts of a plant. Exemplary types of tissue cultures are protoplasts, calli, plant clumps, and plant cells that can generate tissue culture that are intact in plants or parts of plants, such as embryos, pollen, flowers, seeds, pods, leaves, stems, roots, root tips, anthers, and the like. Means for preparing and maintaining plant tissue culture are well known in the art. By way of example, a tissue culture comprising organs has been used to produce regenerated plants. U.S. Pat. Nos. 5,959,185; 5,973,234 and 5,977,445 describe certain techniques, the disclosures of which are incorporated herein by reference.

As used herein, the term “plant” includes plant cells, plant protoplasts, plant cells of tissue culture from which rice plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants, such as pollen, flowers, embryos, ovules, seeds, pods, leaves, stems, pistils, anthers and the like. Thus, another aspect of this invention is to provide for cells which upon growth and differentiation produce a cultivar having essentially all of the physiological and morphological characteristics of L-207.

The present invention contemplates a rice plant regenerated from a tissue culture of a variety (e.g., L-207) or hybrid plant of the present invention. As is well known in the art, tissue culture of rice can be used for the in vitro regeneration of a rice plant. Tissue culture of various tissues of rice and regeneration of plants therefrom is well known and widely published. For example, reference may be had to Chu, Q. R., et al., (1999) “Use of bridging parents with high anther culturability to improve plant regeneration and breeding value in rice”, Rice Biotechnology Quarterly 38:25-26; Chu, Q. R., et al., (1998), “A novel plant regeneration medium for rice anther culture of Southern U.S. crosses”, Rice Biotechnology Quarterly 35:15-16; Chu, Q. R., et al., (1997), “A novel basal medium for embryogenic callus induction of Southern US crosses”, Rice Biotechnology Quarterly 32:19-20; and Oono, K., “Broadening the Genetic Variability By Tissue Culture Methods”, Jap. J. Breed. 33 (Suppl. 2), 306-307, illus. 1983. Thus, another aspect of this invention is to provide cells which upon growth and differentiation produce rice plants having the physiological and morphological characteristics of variety L-207.

Duncan, et al., Planta 165:322-332 (1985) reflects that 97% of the plants cultured that produced callus were capable of plant regeneration. Subsequent experiments with both cultivars and hybrids produced 91% regenerable callus that produced plants. In a further study in 1988, Songstad, et al., Plant Cell Reports 7:262-265 (1988), reports several media additions that enhance regenerability of callus of two cultivars. Other published reports also indicated that “non-traditional” tissues are capable of producing somatic embryogenesis and plant regeneration. K. P. Rao et al., Maize Genetics Cooperation Newsletter, 60:64-65 (1986), refers to somatic embryogenesis from glume callus cultures and B. V. Conger, et al., Plant Cell Reports, 6:345-347 (1987) indicates somatic embryogenesis from the tissue cultures of corn leaf segments. Thus, it is clear from the literature that the state of the art is such that these methods of obtaining plants are routinely used and have a very high rate of success. Thus, another aspect of this invention is to provide cells which upon growth and differentiation produce rice plants having the physiological and morphological characteristics of rice cultivar L-207.

The utility of rice cultivar L-207 also extends to crosses with other species. Commonly, suitable species will be of the family Graminaceae, and especially of the genera Zea, Tripsacum, Croix, Schlerachne, Polytoca, Chionachne, and Trilobachne, of the tribe Maydeae.

Additional Breeding Methods

Although specific breeding objectives vary somewhat in the different regions, increasing yield is a primary objective in all programs. Grain yield of rice is determined by the number of panicles per unit area, the number of fertile florets per panicle, and grain weight per floret. Increases in any or all of these yield components may provide a mechanism to obtain higher yields. Heritable variation exists for all of these components, and breeders may directly or indirectly select for increases in any of them.

There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety an improved combination of desirable traits from the parental germplasm. These important traits may include higher seed yield, resistance to diseases and insects, better stems and roots, tolerance to low temperatures, and better grain quality including improve physical appearance, cooking and taste characteristics, and milling yield (% whole kernel milled rice or head rice and % total milled rice).

Choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of cultivar used commercially (e.g., F₁ hybrid cultivar, pureline cultivar, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection, or a combination of these methods.

The complexity of inheritance influences choice of the breeding method. Backcross breeding is used to transfer one or a few favorable genes for a highly heritable trait into a desirable cultivar. This approach has been used extensively for breeding disease-resistant cultivars. Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination, and the number of hybrid offspring from each successful cross.

Each breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful cultivars produced per unit of input (e.g., per year, per dollar expended, etc.).

Promising advanced breeding lines are thoroughly tested and compared to appropriate standards in environments representative of the commercial target area(s) for three or more years. The best lines are candidates for new commercial cultivars; those still deficient in a few traits may be used as parents to produce new populations for further selection.

These processes, which lead to the final step of marketing and distribution, usually take from 8 to 12 years from the time the first cross is made and may rely on the development of improved breeding lines as precursors. Therefore, development of new cultivars is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.

A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior plant is to observe its performance relative to other experimental plants and to a widely grown standard cultivar. If a single observation is inconclusive, replicated observations provide a better estimate of its genetic worth.

The goal of rice plant breeding is to develop new, unique and superior rice cultivars and hybrids. The breeder initially selects and crosses two or more parental lines, followed by self-pollination and selection, producing many new genetic combinations. The breeder can theoretically generate billions of different genetic combinations via crossing, selfing and mutations. The breeder has no direct control at the cellular level. Therefore, two breeders will never develop the same line, or even very similar lines, having the same rice traits.

Each year, the plant breeder selects the germplasm to advance to the next generation. This germplasm is grown under unique and different geographical, climatic and soil conditions and further selections are then made, during and at the end of the growing season. The cultivars which are developed are unpredictable. This unpredictability is because the breeder's selection occurs in unique environments, with no control at the DNA level (using conventional breeding procedures), and with millions of different possible genetic combinations being generated. A breeder of ordinary skill in the art cannot predict the final resulting lines he develops, except possibly in a very gross and general fashion. The same breeder cannot produce the same cultivar twice by using the exact same original parents and the same selection techniques. This unpredictability results in the expenditure of large amounts of research monies to develop superior new rice cultivars.

The development of new rice cultivars requires the development and selection of rice varieties, the crossing of these varieties and selection of superior hybrid crosses. The hybrid seed is produced by manual crosses between selected male-fertile parents or by using male sterility systems. These hybrids are selected for certain single gene traits such as semi-dwarf plant type, pubescence, awns, and apiculus color which indicate that the seed is truly a hybrid. Additional data on parental lines, as well as the phenotype of the hybrid, influence the breeder's decision whether to continue with the specific hybrid cross.

Pedigree breeding and recurrent selection breeding methods are used to develop cultivars from breeding populations. Breeding programs combine desirable traits from two or more cultivars or various broad-based sources into breeding pools from which cultivars are developed by selfing and selection of desired phenotypes. The new cultivars are evaluated to determine which have commercial potential.

Pedigree breeding is used commonly for the improvement of self-pollinating crops. Two parents which possess favorable, complementary traits are crossed to produce an F₁. An F₂ population is produced by selfing one or several F₁'s. Selection of the best individuals may begin with evaluation of F₁ plants, continue with selection of F₂ plants, and on in the F₃, where the best individuals in the best families are selected and advanced. Replicated testing of families can begin in the F₄ generation to improve the effectiveness of selection for traits with low heritability. At an advanced stage of inbreeding (i.e., F₆ and F₇), the best lines or mixtures of phenotypically similar lines are tested for potential release as new cultivars.

Mass and recurrent selections can be used to improve populations of either self- or cross-pollinating crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued.

Backcross breeding has been used to transfer genes for a simply inherited, highly heritable trait into a desirable homozygous cultivar or inbred line which is the recurrent parent. The source of the trait to be transferred is called the donor parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent. After the initial cross, individuals possessing the phenotype of the donor parent are selected and repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent.

The single-seed descent procedure in the strict sense refers to planting a segregating population, harvesting a sample of one seed per plant, and using the one-seed sample to plant the next generation. When the population has been advanced from the F₂ to the desired level of inbreeding, the plants from which lines are derived will each trace to different F₂ individuals. The number of plants in a population declines each generation due to failure of some seeds to germinate or some plants to produce at least one seed. As a result, not all of the F₂ plants originally sampled in the population will be represented by a progeny when generation advance is completed.

In a multiple-seed procedure, rice breeders commonly harvest one or more seeds from each plant in a population and thresh them together to form a bulk. Part of the bulk is used to plant the next generation and part is put in reserve. The procedure has been referred to as modified single-seed descent or the pod-bulk technique.

The multiple-seed procedure has been used to save labor at harvest. It is considerably faster to thresh panicles with a machine than to remove one seed from each by hand for the single-seed procedure. The multiple-seed procedure also makes it possible to plant the same number of seeds of a population each generation of inbreeding. Enough seeds are harvested to make up for those plants that did not germinate or produce seed.

Mutation breeding is another method of introducing new traits into rice lines. Mutations that occur spontaneously or are artificially induced can be useful sources of variability for a plant breeder. The goal of artificial mutagenesis is to increase the rate of mutation for a desired characteristic. Mutation rates can be increased by many different means including temperature, long-term seed storage, tissue culture conditions, radiation (such as X-rays, Gamma rays, neutrons, Beta radiation, or ultraviolet radiation), chemical mutagens (such as base analogs like 5-bromo-uracil), alkylating agents (such as sulfur mustards, nitrogen mustards, epoxides, ethyleneamines, sulfates, sulfonates, sulfones, or lactones), azide, hydroxylamine, nitrous acid or acridines. Once a desired phenotype is observed the genetic mutation responsible for that trait may then be incorporated into existing germplasm by traditional breeding techniques. Details of mutation breeding can be found in Principles of Cultivar Development by Fehr, Macmillan Publishing Company, 1993.

Descriptions of other breeding methods that are commonly used for different traits and crops can be found in one of several reference books (e.g., Allard, 1960; Simmonds, 1979; Sneep et al., 1979; Fehr, 1987; Marshall and Wadsworth, 1994; Champagne, 2004).

Genetic Analysis

In addition to phenotypic observations, the genotype of a plant can also be examined. There are many laboratory-based techniques available for the analysis, comparison and characterization of plant genotype; among these are Isozyme Electrophoresis, Restriction Fragment Length Polymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs), Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNA Amplification Fingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs), Amplified Fragment Length polymorphisms (AFLPs), Simple Sequence Repeats (SSRs—which are also referred to as Microsatellites), and Single Nucleotide Polymorphisms (SNPs).

Isozyme Electrophoresis and RFLPs have been widely used to determine genetic composition. Shoemaker and Olsen (Molecular Linkage Map of Soybean (Glycine max), pp. 6.131-6.138 in S. J. O'Brien (ed.) Genetic Maps: Locus Maps of Complex Genomes, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1993)) developed a molecular genetic linkage map that consisted of 25 linkage groups with about 365 RFLP, 11 RAPD, three classical markers, and four isozyme loci. See also, Shoemaker, R. C., RFLP Map of Soybean, pp. 299-309, in Phillips, R. L. and Vasil, I. K. (eds.), DNA-Based Markers in Plants, Kluwer Academic Press, Dordrecht, the Netherlands (1994).

The invention further provides a method of determining the genotype of a plant of rice cultivar L-207, or a first generation progeny thereof, which may comprise obtaining a sample of nucleic acids from said plant and detecting in said nucleic acids a plurality of polymorphisms. This method may additionally comprise the step of storing the results of detecting the plurality of polymorphisms on a computer readable medium. The plurality of polymorphisms are indicative of and/or give rise to the expression of the morphological and physiological characteristics of rice cultivar L-207.

With any of the genotyping techniques mentioned herein, polymorphisms may be detected when the genotype and/or sequence of the plant of interest is compared to the genotype and/or sequence of one or more reference plants. The polymorphism revealed by these techniques may be used to establish links between genotype and phenotype. The polymorphisms may thus be used to predict or identify certain phenotypic characteristics, individuals, or even species. The polymorphisms are generally called markers. It is common practice for the skilled artisan to apply molecular DNA techniques for generating polymorphisms and creating markers. The polymorphisms of this invention may be provided in a variety of mediums to facilitate use, e.g. a database or computer readable medium, which may also contain descriptive annotations in a form that allows a skilled artisan to examine or query the polymorphisms and obtain useful information.

SSR technology is currently the most efficient and practical marker technology; more marker loci can be routinely used and more alleles per marker locus can be found using SSRs in comparison to RFLPs. For example, Diwan and Cregan described a highly polymorphic microsatellite locus in soybean with as many as 26 alleles. Diwan, N. and Cregan, P. B., Theor. Appl. Genet., 95:22-225 (1997). SNPs may also be used to identify the unique genetic composition of the invention and progeny varieties retaining that unique genetic composition. Various molecular marker techniques may be used in combination to enhance overall resolution.

Molecular markers, which include markers identified through the use of techniques such as Isozyme Electrophoresis, RFLPs, RAPDs, AP-PCR, DAF, SCARs, AFLPs, SSRs, and SNPs, may be used in plant breeding. One use of molecular markers is Quantitative Trait Loci (QTL) mapping. QTL mapping is the use of markers which are known to be closely linked to alleles that have measurable effects on a quantitative trait. Selection in the breeding process is based upon the accumulation of markers linked to the positive effecting alleles and/or the elimination of the markers linked to the negative effecting alleles from the plant's genome.

Molecular markers can also be used during the breeding process for the selection of qualitative traits. For example, markers closely linked to alleles or markers containing sequences within the actual alleles of interest can be used to select plants that contain the alleles of interest during a backcrossing breeding program. The markers can also be used to select toward the genome of the recurrent parent and against the markers of the donor parent. This procedure attempts to minimize the amount of genome from the donor parent that remains in the selected plants. It can also be used to reduce the number of crosses back to the recurrent parent needed in a backcrossing program. The use of molecular markers in the selection process is often called genetic marker enhanced selection or marker-assisted selection. Flanking markers that are tightly linked to target genes can be used for selection and are sometimes more efficient than direct selection for the target genes. Use of flanking markers on either side of the locus of interest during marker assisted selection increases the probability that the desired gene is selected. Molecular markers may also be used to identify and exclude certain sources of germplasm as parental varieties or ancestors of a plant by providing a means of tracking genetic profiles through crosses.

Particular markers used for these purposes are not limited to the set of markers disclosed herein, but may include any type of marker and marker profile which provides a means of distinguishing varieties. In addition to being used for identification of rice cultivar L-207, a hybrid produced through the use of rice cultivar L-207, and the identification or verification of pedigree for progeny plants produced through the use of rice cultivar L-207, a genetic marker profile is also useful in developing a locus conversion of rice cultivar L-207.

Means of performing genetic marker profiles using SNP and SSR polymorphisms are well known in the art. SNPs are genetic markers based on a polymorphism in a single nucleotide. A marker system based on SNPs can be highly informative in linkage analysis relative to other marker systems in that multiple alleles may be present.

Proper testing should detect any major faults and establish the level of superiority or improvement over current cultivars. In addition to showing superior performance, there must be a demand for a new cultivar that is compatible with industry standards or which creates a new market. The introduction of a new cultivar will incur additional costs to the seed producer, the grower, processor and consumer; for special advertising and marketing, altered seed and commercial production practices, and new product utilization. The testing preceding release of a new cultivar should take into consideration research and development costs as well as technical superiority of the final cultivar. For seed-propagated cultivars, it must be feasible to produce seed easily and economically.

This invention also is directed to methods for producing a rice plant by crossing a first parent rice plant with a second parent rice plant wherein the first or second parent rice plant is a rice plant of the variety L-207. Further, both first and second parent rice plants can come from the rice variety L-207. Thus, any such methods using the rice variety L-207 are part of this invention: selfing, backcrosses, hybrid production, crosses to populations, and the like. All plants produced using rice variety L-207 as a parent are within the scope of this invention, including those developed from varieties derived from rice variety L-207. Advantageously, the rice variety could be used in crosses with other, different, rice plants to produce the first generation (F₁) rice hybrid seeds and plants with superior characteristics. The variety of the invention can also be used for transformation where exogenous genes are introduced and expressed by the variety of the invention. Genetic variants created either through traditional breeding methods using variety L-207 or through transformation of L-207 by any of a number of protocols known to those of skill in the art are intended to be within the scope of this invention.

The following describes breeding methods that may be used with cultivar L-207 in the development of further rice plants. One such embodiment is a method for developing an L-207 progeny rice plant in a rice plant breeding program comprising: obtaining the rice plant, or a part thereof, of cultivar L-207 utilizing said plant or plant part as a source of breeding material and selecting an L-207 progeny plant with molecular markers in common with L-207 and/or with morphological and/or physiological characteristics selected from the characteristics listed in Table 1. Breeding steps that may be used in the rice plant breeding program include pedigree breeding, back crossing, mutation breeding, and recurrent selection. In conjunction with these steps, techniques such as RFLP-enhanced selection, genetic marker enhanced selection (for example SSR markers) and the making of double haploids may be utilized.

Another method involves producing a population of cultivar L-207 progeny rice plants, comprising crossing cultivar L-207 with another rice plant, thereby producing a population of rice plants, which, on average, derive 50% of their alleles from cultivar L-207. A plant of this population may be selected and repeatedly selfed or sibbed with a rice cultivar resulting from these successive filial generations. One embodiment of this invention is the rice cultivar produced by this method and that has obtained at least 50% of its alleles from cultivar L-207.

One of ordinary skill in the art of plant breeding would know how to evaluate the traits of two plant varieties to determine if there is no significant difference between the two traits expressed by those varieties. For example, see Fehr and Walt, Principles of Cultivar Development, p 261-286 (1987). Thus the invention includes rice cultivar L-207 progeny rice plants comprising a combination of at least two L-207 traits selected from the group consisting of those listed in Table 1 or the L-207 combination of traits listed in the Summary of the Invention, so that said progeny rice plant is not significantly different for said traits than rice cultivar L-207 as determined at the 5% significance level when grown in the same environment. Using techniques described herein, molecular markers may be used to identify said progeny plant as a L-207 progeny plant. Mean trait values may be used to determine whether trait differences are significant, and preferably the traits are measured on plants grown under the same environmental conditions. Once such a variety is developed its value is substantial since it is important to advance the germplasm base as a whole in order to maintain or improve traits such as yield, disease resistance, pest resistance, and plant performance in extreme environmental conditions.

Progeny of cultivar L-207 may also be characterized through their filial relationship with rice cultivar L-207, as for example, being within a certain number of breeding crosses of rice cultivar L-207. A breeding cross is a cross made to introduce new genetics into the progeny, and is distinguished from a cross, such as a self or a sib cross, made to select among existing genetic alleles. The lower the number of breeding crosses in the pedigree, the closer the relationship between rice cultivar L-207 and its progeny. For example, progeny produced by the methods described herein may be within 1, 2, 3, 4, 5, 6 or 7 breeding crosses of rice cultivar L-207.

The seed of rice cultivar L-207, the plant produced from the cultivar seed, the hybrid rice plant produced from the crossing of the cultivar, hybrid seed, and various parts of the hybrid rice plant and transgenic versions of the foregoing, can be utilized for human food, livestock feed, and as a raw material in industry.

Tables

Table 2 shows the results of the University of California Cooperative Extension Statewide Yield Tests averaged over locations and years (2012 to 2013, and 2015) for rice cultivar L-207 compared to current California long-grain variety L-206 (U.S. Pat. No. 7,579,531 and U.S. PVP No. 200700081) and the widely grown medium-grain M-206 (U.S. Pat. No. 6,911,589 and U.S. PVP No. 200300180). The test plots were 10×20 foot plots and tests were performed in four replications at the Rice Experiment Station (RES) in Biggs, Calif., and in commercial growers' fields in Sutter County, and Yolo County. Column 1 shows the agronomic trait, columns 2-4 show the rice varieties. In Table 2, rows 2-6 show the seedling vigor score, the days to 50% heading, the plant height in centimeters, percent lodging of the plots, and harvest moisture of the plots, respectively, from RES, Sutter, and Yolo tests, and rows 7-9 show cold tolerance greenhouse blanking percent, the stem rot score, and the aggregate sheath spot score, respectively, all collected from RES. Seedling vigor score is a visual score where a score of 1 is poor and a score of 5 is excellent. A stem rot score of 0 indicates no damage, whereas a stem rot score of 10 equals all plants killed. The aggregate sheath spot score indicates the number of top leaves killed by aggregate sheath spot. An asterisk indicates that the data is significantly different from that of L-206 at the 0.05 probability level.

TABLE 2 Characteristic L-207 L-206 M-206 Seedling Vigor Score    4.9* 4.7    4.9* Days to 50% Heading  85* 81 81 Plant Height (cm) 102* 87 99 Lodging (%)  2 11  18* Harvest Moisture (%) 14 16  19* Greenhouse Blanking (%)  8* 15  8* Stem Rot Score    4.6* 5.6   5.0 Aggregate Sheath Spot Score    1.8* 2.8   2.5

As shown in Table 2, L-207 is distinguished from L-206 in that L-207 had a higher seedling vigor score, averaged 4 days longer to 50% heading, and had lower stem rot and aggregate sheath spot scores than L-206.

Table 3 shows the grain yield performance of rice cultivar L-207 compared to current California long-grain variety L-206, and the widely grown medium-grain M-206 in the very early group of the University of California Cooperative Extension Statewide Yield Tests in 2012, 2013, and 2015. Test locations included the Rice Experiment Station (RES) in Biggs, Sutter and Yolo counties. Row 1 shows test location, row 2 shows the variety, rows 3-5 show the grain yield in pounds per acre for 2015, 2013, and 2012 at RES, Sutter, Colusa and Yolo, respectively, and row 6 shows the overall average variety yield in pounds per acre for all locations. An asterisk indicates that the data is significantly different from that of L-207 at the 0.05 probability level.

TABLE 3 RES Sutter Yolo Year L-207 L-206 M-206 L-207 L-206 M-206 L-207 L-206 M-206 2015 9740  8910*  9350  10880 9820* 9900* 8670 7740* 7490* 2013 9880  9970   8610* 10350 9700* 9710* 10490 9000* 9790* 2012 10290 10020  10420  10040 9570* 9320* 10710 9060* 9900* Mean 9970  9630   9460* 10420 9700* 9640* 9960 8600* 9060*

As shown in Table 3, rice cultivar L-207 had a consistent yield advantage over L-206 at the cooler location of Yolo County, which indicates a wider adaptability of this variety for California rice production.

Table 4 shows average yields of rice cultivar L-207 as compared to rice cultivars L-206 and M-206 at additional University of California Cooperative Extension Statewide Yield Test locations during 2015. Column 1 shows the location of the test and columns 2-4 show the varieties and their average yields in pounds per acre at that location. An asterisk indicates that the data is significantly different from that of L-207 at the 0.05 probability level.

TABLE 4 Location L-207 L-206 M-206 RES 10000 9440  9370  Colusa 11160 9940* 9850* Yuba 10480 9840  9940  Butte  9130 9810* 9370  Glenn 10830 9910* 9620* Mean 10320 9790* 9630*

As shown in Table 4, yields of L-207 at the additional locations during 2015 were 5.4% higher than L-206.

Table 5 shows grain dimension of milled kernels of rice cultivar L-207, L-206 and a commercial brand from Southern US, Mahatma Brand. Column 1 shows the variety, column 2 shows the length in mm, column 3 shows the width in mm, and column 4 shows the length to width (L/W) ratio. An asterisk indicates that the data is significantly different from that of L-207 at the 0.05 probability level.

TABLE 5 Variety Length (mm) Width (mm) L/W Ratio L-207 7.12 2.05 3.47 L-206 7.04 2.10 3.35 Mahatma Brand  6.59* 2.21  2.98*

As shown in Table 5, milled rice kernels of rice cultivar L-207 are similar to L-206 and longer than the commercial brand rice from Southern US.

Table 6 shows the head rice yields determined from sequential harvest moistures samples at RES during 2012 to 2015. The year and variety are listed in columns 1 and 2 and the head rice yield percent for specific harvest dates are listed in columns 3-6. Harvest moisture values are in parentheses.

TABLE 6 Year Variety Head Rice Yield Percent 2015 18 Sep. 22 Sep. 25 Sep. 29 Sep. L-206 59 (21) 62 (18) 59 (17) L-207 63 (18) 61 (15) 67 (14) 2013 13 Sep. 17 Sep. 20 Sep. 24 Sep. L-206 59 (17) 57 (15) 54 (15) 51 (16) L-207 63 (17) 63 (16) 60 (14) 59 (15) 2012 1 Oct. 6 Oct. 10 Oct. 15 Oct. L-206 60 (20) 59 (19) 62 (17) 61 (15) L-207 60 (19) 63 (19) 64 (18) 66 (17)

As shown in Table 6, over a span of 7 to 10 days, head rice yields remained stable ranging between 63 to 67 percent for L-207 versus 59 to 62 percent for L-206 in 2015. Similar differences were observed in 2012 and 2013. The average head rice yields of L-207 were significantly higher than L-206 at 63% and 59%, respectively.

Table 7 shows that the apparent amylose content of rice cultivar L-207 is the same as L-206 and similar to the traditional southern long-grain varieties, averaging 23.2 percent. Rice cultivars L-206 and L-207 both have intermediate type alkali spreading values. The pasting properties of L-207 are not significantly different from L-206 and Mahatma Brand from Southern US as shown by RVA data. Even though RVA values are slightly lower for rice cultivar L-207, the setback value which is a significant indicator of the softness and texture of cooked rice is similar to Mahatma Brand. Cooked rice of L-207 and L-206 was found to be similar by taste panelists and two marketing organizations. Laboratory analysis of 2015 samples provided by the USDA-ARS Rice Quality Lab, Stuttgart, Ark. In Table 7, column 1 shows the variety, column 2 shows the percent amylose, column 3 shows the alkali score, column 4 shows the peak value, column 5 shows the trough value, column 6 shows the final viscosity, and column 7 shows the setback from peak.

TABLE 7 RVA % Alkali Final Setback Variety Amylose Score Peak Trough Viscosity from Peak L-207 23.2 4 251 130 265 14 L-206 22.3 3.7 267 148 293 26 Mahatma 22.6 4 275 152 290 15 Brand

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. For example, if the range 10-15 is disclosed, then 11, 12, 13, and 14 are also disclosed. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Deposit Information

A deposit of the California Cooperative Rice Research Foundation, Inc. proprietary Rice Cultivar L-207 disclosed above and recited in the appended claims has been made with the American Type Culture Collection (ATCC), 10801 University Boulevard, Manassas, Va. 20110 under the terms of the Budapest Treaty. The date of deposit was Jan. 5, 2017. The deposit of 2,500 seeds was taken from the same deposit maintained by California Cooperative Rice Research Foundation, Inc. since prior to the filing date of this application. All restrictions will be irrevocably removed upon granting of a patent, and the deposit is intended to meet all of the requirements of 37 C.F.R. §§ 1.801-1.809. The ATCC Accession Number is PTA-123757. The deposit will be maintained in the depository for a period of thirty years, or five years after the last request, or for the enforceable life of the patent, whichever is longer, and will be replaced as necessary during that period.

While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope. 

What is claimed is:
 1. A seed of rice cultivar L-207, wherein a representative sample of seed of said cultivar has been deposited under ATCC Accession No. PTA-123757.
 2. A rice plant, or a part thereof, produced by growing the seed of claim
 1. 3. A tissue culture of cells produced from the plant of claim 2, wherein said cells of the tissue culture are produced from a plant part selected from the group consisting of leaf, pollen, embryo, cotyledon, hypocotyl, meristematic cell, root, root tip, pistil, anther, flower, stem, glumes and panicle.
 4. A protoplast produced from the plant of claim
 2. 5. A protoplast produced from the tissue culture of claim
 3. 6. A rice plant regenerated from the tissue culture of claim 3, wherein the plant has all of the morphological and physiological characteristics of rice cultivar L-207 listed in Table
 1. 7. A method for producing an F₁ hybrid rice seed, wherein the method comprises crossing the plant of claim 2 with a different rice plant and harvesting the resultant F₁ hybrid rice seed.
 8. A hybrid rice seed produced by the method of claim
 7. 9. A hybrid rice plant, or a part thereof, produced by growing said hybrid rice seed of claim
 8. 10. A method of producing an herbicide resistant rice plant, wherein the method comprises transforming the rice plant of claim 2 with a transgene, wherein the transgene confers resistance to an herbicide selected from the group consisting of imidazolinone, sulfonylurea, glyphosate, glufosinate, L-phosphinothricin, triazine and benzonitrile.
 11. An herbicide resistant rice plant produced by the method of claim
 10. 12. A method of producing an insect resistant rice plant, wherein the method comprises transforming the rice plant of claim 2 with a transgene that confers insect resistance.
 13. An insect resistant rice plant produced by the method of claim
 12. 14. The rice plant of claim 13, wherein the transgene encodes a Bacillus thuringiensis endotoxin.
 15. A method of producing a disease resistant rice plant, wherein the method comprises transforming the rice plant of claim 2 with a transgene that confers disease resistance.
 16. A disease resistant rice plant produced by the method of claim
 15. 17. A method of producing a rice plant with modified fatty acid metabolism or modified carbohydrate metabolism, wherein the method comprises transforming the rice plant of claim 2 with a transgene encoding a protein selected from the group consisting of fructosyltransferase, levansucrase, alpha-amylase, invertase and starch branching enzyme or DNA encoding an antisense of stearyl-ACP desaturase.
 18. A rice plant having modified fatty acid metabolism or modified carbohydrate metabolism produced by the method of claim
 17. 19. A method of introducing a desired trait into rice cultivar L-207, wherein the method comprises: (a) crossing a L-207 plant, wherein a representative sample of seed was deposited under ATCC Accession No. PTA-123757, with a plant of another rice cultivar that comprises a desired trait to produce progeny plants, wherein the desired trait is selected from the group consisting of male sterility, herbicide resistance, insect resistance, abiotic stress tolerance, modified fatty acid metabolism, modified carbohydrate metabolism and resistance to bacterial disease, fungal disease or viral disease; (b) selecting one or more progeny plants that have the desired trait; (c) backcrossing the selected progeny plants with the L-207 plants to produce backcross progeny plants; (d) selecting for backcross progeny plants that have the desired trait; and (e) repeating steps (c) and (d) three or more times to produce selected fourth or higher backcross progeny plants that comprise the desired trait.
 20. A plant produced by the method of claim 19, wherein the plant has the desired trait and otherwise all of the physiological and morphological characteristics of rice cultivar L-207 listed in Table
 1. 21. The plant of claim 20, wherein the desired trait is herbicide resistance and the resistance is conferred to an herbicide selected from the group consisting of imidazolinone, sulfonylurea, glyphosate, glufosinate, L-phosphinothricin, triazine and benzonitrile.
 22. The plant of claim 20, wherein the desired trait is insect resistance and the insect resistance is conferred by a transgene encoding a Bacillus thuringiensis endotoxin.
 23. The plant of claim 20, wherein the desired trait is modified fatty acid metabolism or modified carbohydrate metabolism and said desired trait is conferred by a nucleic acid encoding a protein selected from the group consisting of fructosyltransferase, levansucrase, alpha-amylase, invertase and starch branching enzyme or DNA encoding an antisense of stearyl-ACP desaturase.
 24. The plant of claim 20, wherein the desired trait is abiotic stress tolerance and said desired trait modifies tolerance to drought, flooding, salinity, or temperature change.
 25. A method of introducing the head rice stability trait of rice cultivar L-207 into another rice cultivar, wherein the method comprises crossing a L-207 plant, wherein a representative sample of seed is deposited under ATCC Accession No. PTA-123757, with a plant of another rice cultivar and selecting for progeny plants that have head rice stability.
 26. A rice plant produced by the method of claim 25, wherein said plant has the desired trait and otherwise all of the physiological and morphological traits of rice cultivar L-207.
 27. A method of producing a rice plant with a desired trait, wherein the method comprises introducing a gene mutation via chemical mutagenesis into the rice plant of claim
 2. 28. A rice plant produced by the method of claim 27, wherein said plant has the desired trait and otherwise all of the physiological and morphological traits of rice cultivar L-207 listed in Table
 1. 29. A method of producing a commodity plant product, comprising obtaining the plant of claim 2, or a part thereof, and producing the commodity plant product from said plant or plant part thereof, wherein said commodity plant product is selected from the group consisting of meal, flour, oil, film, packaging, and nutraceutical product. 